Posts don't have an 'add to pool' option individually, so I wasn't that interested in the pool system, but I've discovered that making a pool only takes a few minutes and some resourcefulness.
Just this morning, I was able to make a small pool here:
safebooru.org/index.php?page=pool&s=show&id=201It took me just under a half hour to find and add some fairly tedious posts to the pool. I had one tab open to look through my favorites and other posts of interest, and a second tab open to the pool I was importing stuff to. Beware though that you have to be
very specific when searching for posts because everything that is tagged with your keywords, every result from the search will be added to your pool if you just click 'add' without discretion.
For further instructions, look here:
safebooru.org/index.php?page=help&topic=poolEven though this doesn't completely satisfy your question, it is a start. Sorry. The pools you make can be made to be private or for the public to add and edit. Good luck!